JPS6027008A - Power supply for electrical discharge machining - Google Patents

Abstract

PURPOSE:To attain the machining in a finishing process region of a large area by using a pulse power supply having a small internal impedance. CONSTITUTION:At the starting time of a machining a switch control circuit 27 transmits the ON signal to the 1st drive circuit 19 of the 1st pulse power supply via a signal line 31 and turns a power transistor 18 on to supply a voltage waveform 33 and a machining current 34 between poles of an electrode 28 in the form of the machining voltage. Then the discharge produced between the poles is detected by the circuit 27, and the 1st pulse power supply is turned off with the 2nd pulse power supply turned on respectively. Then a prescribed current 37 is supplied. Hereafter a pause period 38 is secured after a prescribed period to repeat the same action. In such a way, the voltage is impressed between the poles from a power supply having an internal impedance smaller than the inter- pole impedance before the discharge is started. Therefore the sufficient voltage is produced between the poles. In this way, the stable processing is performed even in a finishing process region of a large area.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power source for electric discharge machining that uses a conductive machining fluid as the machining fluid.

A conventional device of this type is shown in FIG.

In the figure, (1) is a DC power supply, (2) is a power transistor, (3) is an oscillator, (4) is a variable resistor that controls the machining current, and (5) is the gap formed by the electrode and workpiece. It is. In general electric discharge machining, an insulating liquid such as mineral oil or kerosene is used as the machining fluid, so the voltage applied between the poles shows the value of BQ when no load is applied, and the voltage and current waveforms during machining are shown in Figure 2 ( a) Voltage waveform of (b) (61(7
1 and the current waveform (8).

However, when using water or a machining fluid that is a mixture of water and an organic compound, the impedance between the electrodes is determined by the distance between the electrode and the workpiece (g), since the machining fluid is conductive.
Assuming that the opposing area between the electrode and the workpiece is (B) and the specific resistance of the machining fluid is (ρ), as shown in FIG.

R=ρ·g --------(1) The impedance decreases as the distance between the electrodes becomes narrower and as the facing area increases. Therefore, the inter-electrode waveform in this case is as shown in Fig. 4. When the inter-electrode voltage is applied, a current based on Ohm's law flows due to the decrease in inter-electrode impedance, resulting in a reactive current (+3). .

The voltage α applied between the electrodes decreases. After that, when discharge starts, the voltage shifts to arc voltage (7) and the machining current shifts to (8). However, when the machining area further increases, the applied voltage does not increase and the voltage waveform becomes only about l[9, as shown in FIG. 5, so no discharge occurs.

Since the reactive current θ→ increases and eventually discharge becomes impossible, when machining a large surface, it is necessary to increase the specific resistance of the machining fluid using an ion exchange resin or the like.

Therefore, it has the disadvantage of being more expensive than kerosene and the like.

The present invention was made in order to eliminate the above-mentioned drawbacks of the conventional electrical discharge machining power supply, and uses a pulsed power supply having an internal resistance lower than the impedance between the machining parts, and which is sufficient to generate a discharge between the machining parts. When it detects that a discharge has occurred between the electrodes, it is turned off, and the pulse power supply that supplies a predetermined machining current waveform is turned on. After that, a power source for electrical discharge machining is provided which controls which series of operations is repeated.

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 6, a7) is the DC power supply of the first pulse power supply, α barrel is the power transistor, (11 is the first drive circuit that drives this power transistor, and (a) is connected to the emitter of the bagu transistor. With a variable resistor,
The internal impedance is adjusted to be smaller than the impedance between the poles. Qo is a diode in the first pulse power supply, 4 is a DC power supply in the second pulse power supply, and 4 is a power transistor.

Q4 is a second drive circuit that drives this power transistor, (c) is a variable resistor that controls the machining current, (c) is a diode in the second pulse power supply, and @ is a switching control device with a built-in oscillator. is an electrode, and @ring is a signal line that detects when a discharge occurs between the electrodes (c).

<9) (52) is the first. This is a signal line to the second power transistor drive circuit.

Next, the operation of the configuration shown in FIG. 6 will be explained with reference to FIG. The switching control device is configured to switch the first pulse power supply to the first pulse power supply at the time of starting.
An on signal is sent to the signal line (31) to the drive circuit member, the power transistor is turned on, and a voltage waveform ("l)t machining current (34) is supplied as a machining voltage between the electrodes (to). If it is not supplied, the machining voltage waveform (55) and machining current waveform (36) will be obtained with only the power source @2.Next, when a discharge occurs between the machining electrodes, the switching control device (c) detects this. , the first pulse power source is turned off, and the second pulse power source is turned off.
Turn on the pulse power.

A predetermined current (37) is applied. After a predetermined time, a pause time (38) is given and the second and first pulse power source is turned on.
Repeat the same action. As described above, until the discharge starts, a voltage is applied between the electrodes by a power source having an internal impedance smaller than the impedance between @, so a sufficient pressure ↑ff is generated between the electrodes.

It is possible to stably perform machining even during large bonding and finishing machining, and the drawbacks of conventional machining can be overcome.

In the above embodiment, a general-purpose electrical discharge machine was described, but the same effect can be obtained with a wire-cut electrical discharge machine.

As described above, according to the present invention, since the first pulse power source having a small internal impedance is used, it is possible to process large areas and finishing areas that were previously impossible to process, and it is inexpensive and practical. It is possible to obtain a power source for electrical discharge machining, which is extremely effective.

[Brief explanation of the drawing]

Figure 81 is a circuit diagram of a conventional electric discharge machine power supply, Figure 2 is a voltage and current waveform diagram of the power supply in Figure 1, Figure 3 is a diagram of the configuration between machining areas when using conductive machining fluid, 4 and 5 are voltage and current waveform diagrams of the conventional example, FIG. 6 is a circuit diagram showing an embodiment of the present invention, and FIG. 7 is an inter-electrode voltage and current waveform diagram of the one shown in FIG. In the figure, α is the DC power supply, Oe is the power transistor, 0 is the first structural circuit, (c) is the DC power supply, (c) is the power transistor, H is the second drive circuit, @ is the switching power supply It is. Agent Masuo Oiwa 1” 1 Mi 1 2nd cause; (Figure 6 Ward Figure 7

Claims (1)

[Claims] A first pulse having an internal impedance smaller than an inter-electrode impedance determined by the distance between the electrode and the workpiece, the opposing area between the electrode and the workpiece, and the specific resistance of the conductive working fluid. With power supply. a second pulse power supply that supplies a predetermined machining current waveform; a detection means that detects that a discharge has occurred between the electrodes after turning on the first pulse power supply; Turn off the first pulse power source, turn on the second pulse power source, and apply a machining current for a predetermined time;
A power source for electrical discharge machining, further comprising a switching circuit that repeatedly controls an operation that provides a predetermined rest time.